Fiber-reinforced composites are one example of the conversion of polymer materials into composites with the goal of application as structural materials that must exhibit high stiffness and high strength. Molecular composites have been proposed for the purpose of realizing the concept of macroscopic fiber-reinforced composites on the molecular level (see, for example, Motowo Takayanagi, Kobunshi, volume 33, page 615 (1984), and Rikio Yokota, Kino Zairyo (Functionand Materials), October issue, page 22 (1988)). Molecular composites consist of polymer with a rigid linear main chain that is molecularly dispersed in a flexible polymer matrix. Since the rigid linear polymer has a very large aspect ratio in the absence of aggregation, a reinforcing activity close to that of a fiber-reinforced composite can theoretically be obtained. Moreover, high-performance materials can be expected because, unlike fibers, there are also no defects at the level of the individual molecules.
Generally, however, the molecular dispersion of rigid linear polymers in flexible polymers is problematic. The various attempts at solving this problem have consisted of for example,
(i) the synthesis of a block copolymer of poly(p-phenylene terephthalamide) (=rigid linear polymer) and nylon 6 (=flexible polymer) followed by dispersion of this block copolymer in nylon 6 (Motowo Takayanagi et al J. Macromol. Sci.-Phys., volume B17, page 591 (1980)), PA1 (ii) metalation of poly(p-phenylene terephthalamidei) (Motowo Takayanagi et al., J. Appl. Polym. Sci., volume 29, page 2547 (1984)), PA1 (iii) polymerization of acrylamide by metalation-generated poly (p-phenylene-terephthalamide) anion with the simultaneous production of a nylon 3 matrix and nylon 3-grafted poly(p-phenylene terephthalamide) (D. R. Moore et al., J. Appl. Polym. Sci., volume 32, page 6299 (1986)), PA1 (iv) blending the polyamic acid precursors of an wholly-aromatic rigid linear polyimide and a polyimide that contains flexible groups in its main chain and then thermally imidizing this blend (Itaru Mira, Kemikaru Enjiniyaringu [Chemical Engineering], August issue, page 69 (1990)), PA1 (v) conducting polymerization to give rigid linear poller in a solution of matrix poller (Kohei Sanui et al, J. Polym. PA1 (vi) utilization of hygrogen bonds (J. C. Painter et al., ACS Polym. Prepr., volume 32, number 1, page 208 (1991)). PA1 (i) 1 to 99.99 weight % of a diorganopolysiloxane PA1 (ii) 0.01 to 99 weight % of a organopolysiloxane-grafted rigid linear aromatic polymer selected from the group consisting of organopolysiloxane-grafted polyimides and organopolysiloxane-grafted polybenzobisoxazoles. PA1 unit (I)/unit (II) molar ratio =100/0 to 30/70, PA1 n=3 to 1,000, PA1 R.sup.1 =C.sub.2 to C.sub.20 oxyalkylene, PA1 R.sup.2 through R.sup.5 =methyl or phenyl, and PA1 R.sup.6 =methyl, n-butyl, sec-butyl, tert-butyl, or phenyl. PA1 unit (XII)/unit (XIII) molar ratio =100/0 to 30/70, PA1 n=3 to 1,000, PA1 R.sup.1 =C.sub.2 to C.sub.20 oxyalkylene, PA1 R.sup.2 through R.sup.5 =methyl or phenyl, PA1 R.sup.6 =methyl, n-butyl, sec-butyl, tert-butyl, or phenyl, ##STR15## wherein, Z is monovalent polysiloxane with formula (III) and mis 1 or 2, ##STR16## where R.sup.8 =oxyalkylene and Q=vinyl, and
Sci.: Part A: Polym. Chem., volume 31, page 597 (1993), and so forth), and
On the other hand, since polydimethylsiloxanes have a low intermolecular cohesive energy, the pure rubber has a low mechanical strength and is typically reinforced by filling with reinforcing silica (see Kunio Itoh (ed.), Shirikoon Handobukku [Silicone Handbook], Nikkan Kogyo Shinbunsha (1990), etc.).
The above-mentioned molecular composites are concerned mainly with plastics, and the use of silicone rubber as a matrix has not been reported up to now. If a rigid linear polymer could be dispersed in a diorganopolysiloxane matrix, it would be possible to provide a novel reinforcing method for silicone rubbers. However, rigid linear polymers and polysiloxanes are inherently incompatible.